[PATCH 2/3] Change the `zero_one ==/!= 0) ? y : z <op> y` patterns to use multiply rather than `(-zero_one) & z`

[Andrew Pinski]

On Wed, Jun 7, 2023 at 4:11 PM Jeff Law <jeffreyalaw@gmail.com> wrote:
>
>
>
> On 6/7/23 17:05, Andrew Pinski wrote:
> > On Wed, Jun 7, 2023 at 3:57 PM Jeff Law via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> >>
> >>
> >>
> >> On 6/7/23 15:32, Andrew Pinski via Gcc-patches wrote:
> >>> Since there is a pattern to convert `(-zero_one) & z` into `zero_one * z` already,
> >>> it is better if we don't do a secondary transformation. This reduces the extra
> >>> statements produced by match-and-simplify on the gimple level too.
> >>>
> >>> gcc/ChangeLog:
> >>>
> >>>        * match.pd (`zero_one ==/!= 0) ? y : z <op> y`): Use
> >>>        multiply rather than negation/bit_and.
> >> Don't you need to check the types in a manner similar to what the A & -Y
> >> -> X * Y pattern does before you make this transformation?
> >
> > No, because the convert is in a different order than in that
> > transformation; a very subtle difference which makes it work.
> >
> > In A & -Y it was matching:
> > (bit_and  (convert? (negate
> > But here we have:
> > (bit_and (negate (convert
> > Notice the convert is in a different location, in the `A & -Y` case,
> > the convert needs to be a sign extending (or a truncation) of the
> > negative value. Here we are converting the one_zero_value to the new
> > type so we get zero_one in the new type and then doing the negation
> > getting us 0 or -1 value.
> THanks for the clarification.  OK for the trunk.

So even though my transformation is correct based on what was done in
match.pd but that was broken already for signed one bit integers:
```
struct s
{
  int t : 1;
};
int f(struct s t, int a, int b)
{
        int bd = t.t;
        if (bd) a|=b;
        return a;
}
```
I am going to withdraw this patch and fix that up first.

Thanks,
Andrew

>
> jeff